Blueprint 408 cooling system questions.

Heating / Cooling / AC

  1. Moparmadness408

    Moparmadness408 Active Member

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    My 408 stroker from blueprint seems to run rather hot. It’s the 465 horsepower one with aluminum heads that utilizes a 360 magnum block. In 85 degree plus heat, it has issues keeping cool. It runs around 210 even cruising at 60 mph. I’m running a 180 degree t-stat. It has an oer radiator for a 1970 340 duster, it has a 17x22 inch core, 4 cores deep, and the tubes are half inch, and it’s copper/brass. It is for an automatic transmission. It currently has a 17 inch 6 blade fan. I am in the process of getting a shroud, and I tried to install the Hayden 2947 fan clutch, and it is too long. So my questions are: are there shorter fan clutches? If not, what electronic fans work well? Is it normal for an engine that hasn’t broken in yet to run hot? And is my radiator an adequate size for this engine?(honestly don’t know if I can fit a much bigger one in this vehicle).
     
  2. jonn6464

    jonn6464 1970 Duster

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    This is just my opinion, no scientific data to back it up (other than real-world operating conditions)...

    There is a big misconception that 3 or 4 core/row radiators offer superior cooling. That name of the game is surface area. In my cars I run a 2 row rad with 1.25" tubes. More fluid is exposed to more cooling surface area. All 3 of them run 170-200, depending on highway or in town driving. Also, my cars show 210-220 on the factory gauge at the straight up and down position. So, that would suggest that the factory thought those temps were okay.

    For reference, the engines I'm talking about are a Mopar 360, a Pontiac 455, and a Ford high performance 302.
     
    Last edited: Aug 9, 2020
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    • famous bob

      famous bob mopar misfit

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      Strongly agree , ditch the 4 core and get the biggest two row 1 1/4'' tube rad. u can get in it , it will be thinner , and u can probly get the short cluth in it , I DID .
      U MEANT 365 H.P. DIDNT YOU ?
       
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      • rumblefish360

        rumblefish360 So close, yet so far away FABO Gold Member

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        Hayden offers shorter clutch’s. There are a few that the big block guys use. IIRC, *I Think* Jaguar came up in the thread I’m thinking of. Do a search here.

        No shroud? Get one:thumbsup: That will help a lot.
        What are you doing for coolant?
        Get another gauge to check against what you have in the car now. I have two Autometer gauges reading a 20* difference on the same engine/car.
         
      • Johnny Mac

        Johnny Mac www.blueprintengines.com FABO Vendor

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        • Johnny Mac

          Johnny Mac www.blueprintengines.com FABO Vendor

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          I agree with this 100%. These cars do NOT have big radiators, and The twin 1.25 tubes in a nice aluminum radiator is (also in my opinion) the best you can get. 4 copper/brass rows are not nearly as efficient, and unless they randomly have success based simply on increased capacity, there are better options like Griffin, or others out there. You have to pay for a good radiator for these cars on the cusp of 500 HP. thats what i've come to know from real world experience also. Of course fans, shrouds, even timing, all come into play, but with only 26 inches to play with...you're starting with a big handicap with a copper/brass.
           
        • famous bob

          famous bob mopar misfit

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        • Moparmadness408

          Moparmadness408 Active Member

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          Okay I’m using the zerex American vehicle formula, it’s orange and it’s pre mixed 50/50. Will a shroud help at higher speeds? I took a heat gun to it, and it reads 203 ish at the thermostat. I filled the radiator up all the Way to the top, and turned on the heater and let it run The gauge does register 180 when I feel the thermostat open.
           
        • gzig5

          gzig5 Well-Known Member

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          A proper shroud will help at all speeds. Without it, the system will not be able to cool at full capacity of the radiator core. You need to be careful selecting an electric fan, they aren't all a sure thing and they put a higher load on the alternator. Cold Case is a forum sponsor and they make nice stuff and can supply the shroud and electric fan package too if you want to go that way. Members may get a discount but you'll need to check with them.
           
        • Johnny Mac

          Johnny Mac www.blueprintengines.com FABO Vendor

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          The $ those 35 ponies take is where the issue lies :p
           
        • Johnny Mac

          Johnny Mac www.blueprintengines.com FABO Vendor

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          Have you topped off the radiator after it has cooled all the way down? Several times?
          Tried leaving the radiator cap off (from cold) and seeing it the t-stat opens properly and you can see the fluid moving? And top it off if low.
          Note, you do have to get the cap on before it hits boiling....so it doesnt geyser.
           
        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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          A working and calibrated vacuum advance will make a huge difference as the rpm rises.
          At cruising rpm, say 2600, your engine could be wanting high 40s to mid 50s for advance. By 2800 it might be wanting hi 50s.
          If you don't give her what she wants, the fuel charge will begin burning too late in the cycle, and will not finish burning before the exhaust valve opens. Therefore, it will have to finish in the headers.
          This causes several problems;
          Firstly, the headers run very hot.
          Second, this destroys the scavenging effect of the headers.
          Third; if the header flange is not tight, and oxygen finds it's way into the header tube, you will experience after-fires, but
          Fourth and the biggest issue is that optimum torque cannot be achieved, so you get terrible fuel mileage.

          To illustrate this;
          Start your engine up and get her warmed up. Put her up on the fast idle cam around 2400 rpm, exact rpm not important so long as it is about 400ish rpm below your cruise rpm. Read your timing.
          Now, just tug on the Vcan and start advancing it. Keep on advancing until the rpm no longer increases.
          Now read your timing again.
          Then return the timing to where you found it, and kick it off the fast idle.
          So what did you find?
          The increasing idle speed showed you that peak torque was not being generated until you gave the engine the timing it wanted.
          Understanding that, it is no stretch to imagine that with the correct amount of cruise timing, your throttle opening can be reduced... which should reduce your fuel-delivery, so now making the same power on less fuel, so up goes your fuel economy, and down goes your operating temperature. BadaBoom!
          So now, it remains for you to establish the correct cruise advance for your engine, and to engineer it to happen.
          Furthermore, you can do the same thing at all popular cruise points; like 30/35 mph in second gear, or 45/50 in third or just pick any rpm of interest to you, and calibrate your curve to deliver, as close as you can, the advance she wants.
           
          Last edited: Aug 9, 2020
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          • Moparmadness408

            Moparmadness408 Active Member

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            What radiator did you get? The 2 row aluminum one for mine doesn’t appear to be any thinner. The thickness is 3 inches and that’s what my current one is.
             
          • jonn6464

            jonn6464 1970 Duster

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            Agree with Johnny Mac, take that rad cap off and fire it up. When you see the fluid moving take note of the temp gauge. Now, make sure you have the front end on jack stands, that will purge any air in the system out of the rad opening. Air in the fluid equals steam and that will drive up the temp.
            There is another school of thought that says go with a 165 degree thermostat. The thinking is that it will open sooner and get fluid moving before temps creep up.
            I use a 165 t-stat on my 455 Firebird, because it has iron heads and Ross flat top pistols (no relief cut in them at all, true flat tops) making around 11:1 compression. So that engine runs warm. But between the t-stat and the 1.25" tubes in the rad, all is good.
             
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            • Moparmadness408

              Moparmadness408 Active Member

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              Ok, so I’ve let it sit, filled the radiator to the top, and have checked it multiple times. The coolant never got low. I decided to go with the griffin cross flow Aluminum radiator the core is 22.5 by 19, the radiator is a total of 27.5 inches wide has the twin 1.25 tubes, and it didn’t make much of a difference. However when I checked the coolant I noticed it was brown, and the color I’m using is bright orange. Do you guys drain the blocks out before shipping them?
               
            • autoxcuda

              autoxcuda Well-Known Member

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              Surprise surprise...the wide 2 row these guys suggested put you in the same place you were before.

              These aftermarket radiators must have some goofy side brackets that are pushing the core too far back.

              Or what is the actual distance between the fan and the radiator core?

              Are you running a thick billet water pump pulley?

              Where did your fan come from? Wonder if it’s too wide

              A stock radiator with a high density fin count core made by a good radiator shop would allow you to run a stock 7 blade fan and the 2947 Hayden clutch and a stock fan shroud. Unless your motor is in the wrong spot.

              These generic aluminum radiators require the purchaser to have the skill to fabricate and engineer:
              -fan shroud for mechanical fan
              or
              -electric fan (preferably OEM) with fabricated mounting and electric supply
               
            • Johnny Mac

              Johnny Mac www.blueprintengines.com FABO Vendor

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              Yes. They are drained. Otherwise they would rust in the bag.
              What fan/shroud is on it now?
              What is "not much better?"
              You say above it was hitting 180 on gauge with tstat open before. That's normal...with a 180 stat. T stats are junk anymore. I have replaced way more than I should have had to in the last few years.
              Did you drain the heater core either time?
              Could be lots of gunk in there.
              When is it hot? Idle? Cruise? Always?
              Does the fan generate enough suction to hold a playing card to the radiator?
              Pretty vague on many, many factors/scenarios.
              We can all take stabs at it, but need a little more info to be more help.
              What's your timing at?
              Vac advance?
               
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              • Car Nut

                Car Nut Mopar Master

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                Have you checked the block temperature with a infrared temperature gun?
                 
              • jimjimjimmy

                jimjimjimmy lobsterman FABO Gold Member

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                if it does not get hotter than 210 why worry .
                 
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                • Moparmadness408

                  Moparmadness408 Active Member

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                  Ok so the coolant wasn’t actually brown. It was starting to get dark outside and it looked brown. I put a filler cap in the upper hose because I thought it was too far above the radiator and when you shine a light in it it’s orange. The radiator did make it run about 5-10 degrees cooler. It also seems to take longer before it gets hot. The car basically runs hot at all times. If you take it out early in the morning when it’s cool the temperature stays around 190-200. I’m running a mechanical advance on my distributer, it’s the msd 8388 I’m using I think the blue springs with the black stop bushing. At idle it 16 degrees, and at 4K rpm, at 34 degrees. The full advance doesn’t kick in until it reaches 4K rpms. Another thing is it also tends to diesel when I shut it off after driving it for a while. If a let it idle for a minute it before shutting it off, it won’t diesel.
                   
                • rumblefish360

                  rumblefish360 So close, yet so far away FABO Gold Member

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                  Dieseling is carb/ignition/fuel related.
                   
                • yellow rose

                  yellow rose Master Of Insanity

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                  That curve is WAY too slow.
                   
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                  • jonn6464

                    jonn6464 1970 Duster

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                    3 things...

                    1) Agree with previous member's post that the curve is off. Play with the timing a bit. Are you running a vacuum line to the carb?
                    2) Swap in a 165 degree t-stat. That way the coolant gets moving sooner and starts cooling at a lower temp.
                    3) if you are running 210 and under, you have nothing to worry about, temperature wise. You still need to get the timing and dizzy dialed in though.
                     
                  • CRUZE 418

                    CRUZE 418 FABO Gold Member FABO Gold Member

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                    You already have the radiator, so it's a little late, the '69 cast iron pump is 3/4" shorter than '70 and up pump. I am trying to get a compatible set up right now for my 418. I think that I will have enough room with the Cold Case Radiator, viscous drive fan and shroud when using the '69 style Milodon pump. If it all fits, after engine start, I will be taking all of the advice given in these posts.
                    Chrysler Parts, used. (old)
                    2863216 18" fan
                    3462108 Viscous Drive
                    16251. Milodon Pump
                    Do not have shroud yet

                    From timing cover to end of drive is 7 3/4".
                     
                  • autoxcuda

                    autoxcuda Well-Known Member

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                    Last edited: Sep 22, 2020
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